In 3GPP (3rd Generation Partnership Project) that is a project aiming to standardize a mobile communication system, the standardization of CoMP (Coordinated Multi-Point) is in progress (see Non Patent Document 1).
The CoMP is a communication mode in which an antenna group arranged in the same place is positioned as one “point” and a plurality of points cooperate with one another to perform communication with a user terminal. A point group that performs communication with the user terminal by using one time-frequency resource is called a CoMP cooperating set.
Incidentally, when a handover procedure from a source cell to a target cell is performed, the user terminal transmits a random access preamble signal to the target cell. A target base station that manages the target cell generates timing information for adjusting a timing at which the user terminal transmits an uplink signal on the basis of a reception timing of the random access preamble signal. Then, a target cell base station transmits, to the user terminal, a random access response including the generated timing information. The user terminal transmits, to the target cell, a connection complete notification indicating that a connection with the target cell is completed on the basis of the notified timing information.